Ferrer will be called up by the Nationals on Friday, Jesse Dougherty of The Washington Post reports.
Ferrer has struggled with his command this summer at Triple-A Rochester, but the 23-year-old relief prospect owns a 3.04 ERA with 235 strikeouts in 192.2 career minor-league innings. He'll probably slide into a middle-relief role initially but could see higher-leverage opportunities after the Nats shed parts at the Aug. 1 trade deadline.